Heat processable photographic elements having water vapor-impermeable protective outer layer



Sept. 23, 1969 P. H. STEWART 3,468,664

HEAT PROCESSABLE PHOTOGRAPHIC ELEMENTS HAVING WATER .VAPOR-IMPERMEABLE PROTECTIVE OUTER LAYER Filed Feb. 20, 1962 sxposune' Sfage v 12 x x MOISTURE wpmwous LAYER gr-57L v.51? HAL 10E, aevaopnva AGENT,

ALKAL/ 1- sup/ 097 l HEA mva $7096 '2 /& 5/L l/Ef? IMAGE PAUL H. STEWART BY Mv/M nrramvsr a AGENT United States Patent 3,468,664 HEAT PROCESSABLE PHOTOGRAPHIC ELEMENTS HAVING WATER VAPOR-IMPERMEABLE PRO- TECTIVE OUTER LAYER Paul H. Stewart, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed Feb. 20, 1962, Ser. No. 174,472 Int. Cl. G03c 5/30, 1/48 U.S. Cl. 96-63 19 Claims ABSTRACT OF THE DISCLOSURE Photographic elements containing a developing composition and having a flexible transparent layer substantially impermeable to water vapor adhered to the outer surface of the emulsion layer, methods for processing the same, and more particularly to such photographic elements adapted to processing with heat in a relatively dry atmosphere.

This invention relates to photographic elements containing silver halide developing agents, methods for processing the same, and more particularly, to such photographic elements adapted to processing with heat in a relatively dry atmosphere.

A common procedure in the photographic art involves exposure of a silver halide emulsion layer to a subject followed by development of the resultant latent image with an alkaline solution of a silver halide developing agent such as hydroquinone to produce a silver image in the regions of the latent image. Fixing and washing steps customarily follow.

It has also been proposed to incorporate the silver halide developing agent into the sensitive element, for example, into the silver halide emulsion layer, in which case development of the exposed emulsion can be initiated merely by application of an alkaline solution. It is also known that in case both the developing agent and the alkali required to activate the developing agent are present in the sensitive element, development of the emulsion can be initiated by merely applying water.

In the Stewart et al. US. patent application Ser. No. 134,014 filed Aug. 5, 1961, is described a photographic process in which a sensitive element, including a silver halide emulsion layer containing a latent image, contiguous silver halide developing agent and alkali, is processed without the use of aqueous or liquid compositions by merely heating the element under relatively dry conditions thereby developing silver images in the emulsion layer.

The sensitive elements used in the Stewart et al. invention included the combination of at least one silver halide emulsion layer, a 3-pyrazolidone silver halide developing agent and an alkaline substance effective to accelerate development of a latent image in the silver halide emulsion in the presence of the developing agent. The element further included a saccharide, particularly a nonreducing oligosaccharide, such as sucrose or rafiinose; and preferably, as an auxiliary developing agent, an ascorbic acid or polyhydric phenol silver halide develop ing agent. Additional ingredients which could be present in the sensitive element were developer preservatives such as sulfite and fog reducers such as mercaptotetrazoles or benzotriazoles. The mentioned alkaline substance, developing agent and saccharide were disposed integral with the sensitive element and contiguous to the silver halide, that is, either directly in the silver halide emulsion or in an elfectively adjacent colloid layer or layers. Thus the primary developing agent, the 3-pyrazolidone compound,

Patented Sept. 23, 1969 could be present in the silver halide emulsion and the auxiliary developing agent, alkali and saccharide in an adjacent colloid layer. Similarly, both developing agents, alkali and saccharide, could be present in a layer underlying or overlying the emulsion on a support. Useful combinations of developer ingredients, included a 3- pyrazolidone developing agent as the sole developing agent, in combination with a saccharide; a 3-pyrazolidone in combination with an ascorbic acid and, if desired, a saccharide, and the combination of a 3-pyrazolidone developing agent, a polyhydric phenol developing agent, and if desired, a saccharide.

The process of the Stewart et al. invention further embodied the steps of recording latent images in the silver halide emulsions in the presence of the developing agents and other ingredients mentioned above, followed by heating the emulsion sufficiently to develop silver images therein. In a representative procedure, the sensitive element containing the mentioned ingredients and a small amount of moisture was exposed to a subject, then subjected to heat by passing over a heated roller at temperatures of the order of 50 to 200 C. As a result a silver image was developed in the emulsion layer. In another procedure, an exposed sensitive element containing the mentioned ingredients was passed at speeds of the order of 10 to 200 feet per minute through a heated chamber so designed that moisture rising from heating of the sensitive element was confined within the chamber and a combination of heat and moisture thus obtained initiated development. The exposed sensitive elements could also be processed by subjecting them to the action of hot air, containing a moderate amount of moisture. Moist steam could be used but it was not required. One disadvantage of that process was that the print could not be viewed as it was developed because the apparatus including the proceSSing chamber abscured the print. If the top of the chamber was removed to afford view of the print during processing, moisture escaped and image quality was greatly reduced.

I have discovered that the sensitive elements described above which contain silver halide and contiguous developing agent and alkali can be viewed while being processed and still produce prints having good photographic quality if the outer surface of the silver halide emulsion layer is provided with a flexible transparent coating resistant to the penetration of water vapor. That is, as mentioned above, the development process requires that a small amount of moisture be present in the sensitive element together with the silver halide developing agent and alkali, in order that the development of the exposed silver halide will proceed upon application of heat. In the Stewart et al. invention it was preferred for best results to confine the moisture to the sensitive element in some manner such as by use of special processing equipment designed to confine the moisture near the surface of the emulsion layer.

According to my invention, when the transparent coatcoating is applied to the surface of the emulsion layer, which coating is resistant to moisture penetration and preferably is substantially impervious to moisture vapor, upon heating the exposed emulsion layer moisture is effectively trapped in the element and development quickly proceeds with the result that prints of good quality are obtained. Thus, the equipment used for heating the sensitive element over a heated surface preferably with the emulsion support in contact therewith with the result that development quickly proceeds and the print can be viewed immediately thereafter.

While useful results can be obtained with other silver halide developing agents having high development activity, the 3-pyrazolidone developing agents are preferred components of the sensitive elements and are unique in their activity in the dry development process of the invention as compared to other silver halide developing agents. Thus, when one sensitive element containing both 1-phenyl-3-pyrazolidone and ascorbic acid and a second element containing both monomethyl-p-aminophenol and hydroquinone are exposed and heated under various conditions, a low density silver image is obtained in the latter element. On the other hand, the 3-pyrazolidone-ascorbic acid system of the invention yields a high density silver image under the same conditions of treatment.

Moreover, it is important that a substantial amount of the 3-pyrazolidone developing agent in addition to the alkali be present in the silver halide emulsion or in a contiguous layer. For example, an emulsion containing no alkali and no more than about two grams of 3-pyrazolidone compound per mole of silver halide, upon exposure and heating yields no visible silver image. When about to 50 grams of 3-pyrazolidone compound per mole of silver halide is present, only a faint visible image is obtained upon heating in the absence of alkali. However in the presence of alkali, about to grams of 3-pyrazolidone per mole of silver halide is suflicient to produce a high density silver image upon heating the latent image. When an auxiliary developing agent such as ascorbic acid or hydroquinone is present in addition to the 3-pyrazolidone compound and a saccharide, as little as five grams of 3-pyrazolidone developing agent per mole of silver halide is sufficient. Of course, if desired, the 3-pyrazolidone-containing emulsions free of alkali may be developed with alkaline solutions containing additional developing agents as Elon and hydroquinone.

The accompanying drawing shows in greatly enlarged cross-sectional view the appearance of a representative sensitive element of the invention at different stages of processing. Equipment particularly useful for heating the sensitive element of the invention is described in the Stewart US. patent application Ser. No. 147,899 filed Oct. 26, 1961 comprising a grooved heated element over which the exposed sensitive element is passed with the emulsion support in contact with the heated surface.

In the element of FIG. 1 of the drawings, layer 10 represents a support such as synthetic resin or cellulose ester, preferably paper, carrying a silver halide emulsion layer 11, a 3-pyrazolidone developing agent and alkali integral and contiguous to the silver halide and, if desired, other ingredients such as the auxiliary developing agent and a saccharide. Layer 12 represents a transparent layer substantially impermeable to moisture such as a cellulose ester or synthetic polymer coating or laminate serving to confine moisture to the element during the heat development step.

As shown in Stage 1 of the drawings, the process of the invention includes the exposure of the sensitive element to a subject to record a latent image in the silver halide in area 13 of layer 11. Thereafter, the element is heated sufliciently to develop a silver image in area 13 as shown in Stage 2. In this process, it will be observed that when the sensitive element is heated, a visible silver image is obtained instantaneously. This result is facilitated by the use in the emulsion layer of silver halides which have short development induction periods, such as fine grain silver bromide emulsions. Emulsion having longer induction periods are useful but require longer application of heat to effect their development in the processes of the invention. Also it has now been found that the use of the moisture impervious layer 12 facilitates the rapid production of a visible silver image in these emulsions, the effect being especially pronounced with the emulsion possessing longer development induction periods.

The 3-pyra2olidone silver halide developing agents, such as those described below, are useful in our invention. The 3-pyrazolidone compounds having the following general Formula I are particularly useful in the sensitive elements.

in which the various R groups reprseent substituents such as hydrogen, alkyl, acyl, heterocyclic or aryl groups, for example, R can be benzothiazolyl or an aryl group of the benzene or naphthalene series, substituted or not. R R R R and R can be hydrogen atoms or alkyl groups of from 1 to 12 carbon atoms or aryl groups such as phenyl and naphthyl, substituted or not. Typical substituents are lower alkyl groups, including haloalkyl, pyidiniumor picolinium-N-alkyl halide, e.g. pyridinium-N- methyl chloride, benzyl, phenyl, 4-methylphenyl, 4-methoxyphenyl, carboxylic acid acyl as acetyl, benzoy, nitrobenzoyl and haloacyl, e.g. chloroacetyl, phenoxy and alkylphenoxy.

The 3-pyrazolidone developing agents of our invention which are used to advantage particularly with gold and sulfur sensitized silver halide emulsions are represented by the following formulas:

, wherein R and R each represent a hydrogen atom or an alkyl group having from about 1 to 12 carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl, secondary butyl, tetriary butyl, amyl, isoamyl, tertiary amyl, hexyl, etc.; and R represents a hydrogen atoms, an alkyl group or a carboxylic acid acyl group such as methyl, ethyl, propyl, isopropyl, butyl, amyl, tertiary amyl, hexyl, chloromethyl, bromomethyl, chloroethyl, chloropropyl, pyridinium-N-methy chloride, pyridinium-N-ethyl chloride, benzyl, etc.; or an aryl group such as phenyl, 4-methylphenyl, 4-methoxyphenyl, acetyl, dichloroacetyl, propionyl, 4-nitrobenzoyl, aryloxy such as 2,4-di-tert, amylphenoxy, and R and R represent alkyl or aryl groups such as above.

The compounds above which contain the acyl substituents R and R are particularly useful because they are developing agent precursors and are not active developing agents until the acyl group has been split off in the presence of alkali. Accordingly, these acyl derivatives in which active positions of the pyrazolidone nucleus are blocked, are very useful in the emulsions especially in the higher concentrations of the order of to 300 gms. per mole of silver halide. When alkali is also present in the sensitive element it may be desirable to segregate it from the acyl derivative to prevent premature release of the active form of the developing agent. The 4-algyl and 4,4-dialkyl substituted compounds behave similarly.

The compounds are not to be confused with S-pyrazolidones such as l-phenyl-S-pyrazolidone.

The following compounds are representative of the 3- pyrazolidone compounds useful for the purposes of our invention.

1) 1-phenyl-3-pyrazolidone (2) 1-p-toly1-3-pyrazolidone (3) 1-phenyl-4-methyl-3pyrazolidone 1-pheny1-2-benzoyl-3-pyrazolidone 1-p-chlorophenyl-3-pyrazolidone 1-phenyl-5-phenyl-3-pyrazolidone (7) 1-m-tolyl-3-pyrazolidone (8) 1-phenyl-5-methyl-3-pyrazolidone (9) 1-p-tolyl-5-phenyl-3 -pyrazolidone (10) l-m-tolyl-3-pyrazolidone 1 1) 1-p-methoxyphenyl-3 -pyrazolidone (12) l-acetamidophenyl-3-pyrazolidone 13) l-phenyl-2-acetyl-4,4-dimethyl-3-pyrazolidone (14) 1-phenyl-4-4-dimethyl-3-pyrazolidone 15 1-m-aminophenyl-4-methyl-4-p ropy1-3 -pyrazolidone ( 16) 1-o-chlorophenyl-4-methyl-4-ethyl-3-pyrazolidone (17) 1-m-acetamidophenyl-4,4-diethyl-3-pyrazolidone (18) 1- p-fi-hydroxyethylphenyl) -4,4-dimethyl-3- pyrazolidone l 9) l-p-hydroxyphenyl-4,4-dimethyl-3-pyrazolidone (20) 1-p-methoxyphenyl-4,4-diethyl-3-pyrazolidone (21 1-p-tolyl-4,4-dimethyl-3-pyrazolidone (22) 1- 7-hydroxy-2-naphthyl -4-methyl-4-n-propyl-3- pyrazolidone (23) 1-p-diphenyl-4,4-dimethyl-3-pyrazolidone (24) 1-(p-B-hydroxyethylphenyl)-3-pyrazolidone (25) 1-o-tolyl-3-pyrazolidone 26) l-o-tolyl-4,4-dimethyl-3 -pyrazolidone 27) l-benzothiazolyl-3 -pyrazolidone (28) 1-phenyl-2-p-nitrobenzoyl-3-pyrazo1idone (29) 1-phenyl-2-carbethoxy-3-pyrazolidone (3 0) 1-phenyl-2- u-2,4-di-t-amylphenoxybutryl -3- pyrazolidone (31 1-phenyl-Z-phenoxyacetyl-4-methyl-3-pyrazolidone (32) 1-phenyl-2-lauroyl-3-pyrazolidone (3 3 1-pheny1-2-acetyl-3-pyra2olidone (34) 1-phenyl-2-chloroacetyl-3-pyrazolidone (3 5 1-phenyl-3-acetyl-4-methyl-3-pyrazolidone (3 6) 1-p-tolyl-2-acetyl-3 -pyrazo1idone (37) 1-p-chlorophenyl-2-acetyl-3-pyrazolidone (41) Enol acetate of l-phenyl-3-pyrazolidone (42) Enol acetate of 4-methyl-1-phenyl-3-pyrazolidone Compounds 1 to 12 can be prepared by the methods described in British Patents 679,677 and 679,678. Compounds 13 to 23 and 26 above are representative of 4,4- dialkyl-3-pyrazolidone compounds useful in this invention and these compounds are described in Allen et al. US. Patent 2,772,282, Nov. 27, 1956.

The w-hydroxyalkylphenyl-3-pyrazolidones in which the alkyl group preferably contains from 1 to 4 carbon atoms, for example, compounds 18 to 24 above, are described in Allen et al. invention and in Reynolds and Tinker US. Patent 2,743,279, Apr. 24, 1956.

Compounds 33 to 35 and 38 to 42 may be prepared as described in US. Ser. No. 134,014 above mentioned.

While the processes of the invention can be carried out with sensitive elements containing a 3-pyrazolidone silver halide developing agent as the sole developing agent, in a preferred embodiment of the invention a 3-pyrazolidone developing agent is used in combination with accorbic acid silver halide developing agent, such as dand lascorbic acids, d-arabo ascorbic acid, iminogluco-ascorbic acid and other ascorbic acids having the formulas shown in James et al., US. Patent 2,688,549, granted Sept. 7, 1954. Alternately, the 3-pyrazolidone developing agents are employed in combination with a polyhydric phenol silver halide developing agent such as hydroquinone, catechol, 4-phenylcatechol or pyrogallol. As mentioned previously, when a 3-pyrazolidone is used in combination with these auxiliary developing agents, appreciably less of the 3-pyrazolidone compound is required in the sensitive element to maintain high development activity and thus produce the silver images with a minimum of heating of the exposed emulsion layer.

The saccharides have previously been employed in a sensitive element in order to improve the stability of the emulsion upon aging for extended periods of time. In the present invention of the saccharides, especially the non-reducing oligosaccharides, such as sucrose and raifinose, permit use of much less developing agent in the freshly coated sensitive element than would be the case if the saccharide were absent. Representative saccharides which may be used are: fructose, glucose, inulin, melezitose, pectin, raffinose, starch, sucrose and trehalose. The non-reducing oligosaccharides such as sucrose and raflinose are especially useful.

Non-reducing has a meaning herein usually applied to saccharides and means that the compounds are members of the class of saccharides which do not reduce alkaline solutions of salts of metals such as copper salts, as present in Fehlings solution, as compared to reducing sugars like fructose.

Useful amounts of the various ingredients in the sensitive elements can be ascertained from the following examples although optimum qualities should be ascertained by experiment under the particular conditions in use. However, 3-pyrazolidone compound such as 1-phenyl-3- pyrazolidone may be used in amounts in excess of about 20 grams per mole of silver halide and when in combination with an auxiliary developing agent such as, ascorbic acid or hydroquinone, an amount in excess of abut 5 grams per mole of silver halide should be used. Quantities of the 3-pyrazolidones in excess of about 50 grams per mole of silver halide may be difiicult to disperse in many silver halide emulsions. However, somewhat larger amounts of from about 50 to 300 grams per mole of silver halide can be used. The saccharides may be used in combination with the pyrazolidones in amounts ranging from about 30 to 1000 grams per mole of silver halide. If too large a quantity is used, crystallization occurs or the emulsion tends to be tacky, depending upon the particular saccharide used. The auxiliary developing agents such as the ascorbic acids may be used in combination with the 3-pyrazolidones in amounts of the order of about 30-600 grams per mole of silver halide and the polyhydric phenol developers such as hydroquinone in the range of about 15 to 75 grams per mole of silver halide.

However, at the higher levels of concentration, the latter developing agent tends to produce more background stain in the prints than desired.

The alkaline materials present in the sensitive elements together with the developing agents include inorganic alkalies such as alkali metal metaborate and carbonate. Organic alkaline materials such as quaternary ammonium bases and amines such as 2-amino-2-methyl-1,3-propane diol can be used. The inorganic alkalies which do not yield volatile bases upon heating are very useful.

As mentioned, the sensitive element should contain a small amount of moisture at the time of heating to develop the image. A useful amount of moisture is that remaining in a sensitized paper, such as prepared in Example l, upon drying and handling at about 75 F. and 30 to 50% RH e.g., about 5 to moisture.

The emulsion addenda described in the Stewart et al. US. patent application Ser. No. 134,014 mentioned, including the noble metal salts, stannous salts, polyamines, optical sensitizing dyes, stabilizing compounds, chemical sensitizing compounds, plasticizers, gelatin hardeners, coating aids and colloid vehicles disclosed therein may be used advantageously in the present emulsions. The silver halide emulsions may be varied considerably and include silver bromide, silver chloride, silver iodide and combinations of these such as chlorobromide, chlorobromoiodide or bromoiodide.

The coatings, which are applied to the emulsion layer to resist penetration of water vapor resulting from heating of the sensitive element, can be applied to the emulsion layer by various methods including coating aqueous or organic solvent solutions or dispersions of organic filmforming polymeric materials upon the emulsion layer or by the lamination of thin transparent polymeric sheets onto the emulsion layers. In one method a thin transparent foil such as cellulose actate sheeting can be merely pressed into contact with the emulsion surface without using any particular adhesive and the cellulose acetate sheet adheres sufiiciently to the emulsion surface to confine the moisture to the emulsion during the heating step. Thus, in those cases where the moisture impervious layer is not permanently adhered to the emulsion layer, it may be desirable following processing to detach the coating in order to allow further photographic operations such as fixing to be performed upon the developed emulsion layer. The lamination of such sheeting onto the emulsion can be performed either prior to or subsequent to exposure of the emulsion layer to the subject. In another procedure illustrated in the examples below, aqueous dispersions or latices containing synthetic polymers resistant to moisture are suitable for coating upon the emulsion layers to provide the same moisture impervious layers.

The following examples will serve to illustrate my invention.

EXAMPLE 1 To a gelatino silver bromoiodide emulsion which was optically sensitized was added, per mole of silver halide, 1.5 gm. 1-pheny1-5-mercaptotetrazole, 640 gm. sucrose, 162 gm. ascorbic acid, 30 gm. 1-phenyl-3-pyrazolidone, 36 gm. sodium sulfite (anhy.) 540 gm. sodium metaborate octahydrate, and 12 gm. potassium bromide. The emulsion was coated on a paper base at a coverage of about 1500 square feet per mole sliver halide. A 50% polyvinylidene chloride latex Resyn 3600 manufactured by the National Starch Company, 750 3rd Ave., New York, N.Y., was adjusted to a pH of 9.5 with 2.5 N NaOH and coated upon the emulsion layer at a coverage of about 7.5 gm. latex per square foot.

The resulting sensitive element appears substantially as shown in Stage 1 of the drawing, the emulsion layer 11 being supplied with the flexible substantially moisture impervious polymeric layer 12 obtained by coating the polymeric latex thereon. Samples of this sensitive paper, and Control samples of the same paper not provided with the polymeric layer, were exposed to a subject then advanced at 3 ft. per minute for a distance of about 4 inches over a curved metal surface heated to 150 C. with the result that silver images quickly became visible. After processing in this manner, the exposed element of Stage 1 appears substantially as shown in Stage 2 the emulsion layer 11 containing the silver image 13. As a result of processing both of the papers, silver images were readily visible in each emulsion layer, but the paper of the invention carrying the transparent polymeric coating 12 upon the emulsion layer had a speed 0.26 relative log E faster, at a densty of 0.1 above fog, than the paper not provided with the polymeric coating.

In a similar manner, the sensitive elements comprising silver halide developing agent and alkali can be coated with latices of various types capable of yielding transparent coatings resistant to moisture penetration, depending upon the moisture repellent properties of the polymeric component of the latex. Thus, polyvinyl ester latices, such as Flexac, a latex containing 50% polyvinyl ester manufactured by the Colton Chemical Company, have been found to be very useful in place of the latex used in Example 1.

EXAMPLE 2 The same ingredients were added to a gelatino silver chlorobromoiodide emulsion as in Example 1, except using 5.0 grams of 1-phenyl-5-mercaptotetrazole, and the emulsion was coated upon a paper base at a coverage of about 1500 sq. ft. per mole of silver halide. A transparent adhesive sheet, Scotch Brand Cellophane Tape, manufactured by Minnesota Mining and Manufacturing Company, St. Paul, Minn., was laminated to the surface of the emulsion layer and strips of the resultant element, together with strips of the Control sample not provided with the adhesive sheet over the emulsion layer, were exposed to a subject and each strip passed over a metal surface heated to 150 C. at different speeds to develop silver images therein with the results shown in the following table:

Paper Travel Speed (it./min.)

0. 5 1. 0 2. 0 3. 0 5. 0 Da of control strips 0. 74 0.76 0. 55 0. 48 0. 38 Dam. of strips laminated to tape 1. 14 1. 12 1. 06 1.02 0.70

From the data in the above table, it will be apparent that with varying amounts of heat represented by the different paper travel speeds, the sensitive element of the invention provided with the adhesive sheet overlying the emulsion layer yielded silver images having substantially greater density. In a similar manner, other transparent adhesive tapes such as the transparent polyester adhesive tape No. 850 sold by the Minnesota Mining and Manufacturing Company can be used in the manner of this example to apply a moisture impervious layer to the emulsion surface.

It has also been found that in processes of the above type, the rate of development may be increased and the background density of the prints improved by the incorporation of a silver halide solvent such as sodium thiosulfate into the sensitive element as follows: A gelatino silver halide emulsion containing sucrose, ascorbic acid, 1-phenyl3pyrazolidone, sodium sulfite, sodium metaborate, potassium bromide and sodium thiosulfate was coated on a peper (or film) base and air dried; also, a control coating with the sodium thiosulfate omitted was made. Imagewise exposed strips of both coatings were then subjected to air saturated with moisture at 100 C. for a time suflicient for the prints to be stable when exposed to actinic light under high relative humidity conditions. The coating containing sodium thiosulfate required a considerably shorter processing time than that required for the control, and the background density of the print was lower than that of the control print. The process can be carried out as shown in detail in the following example.

9 EXAMPLE 3 A gelatino silver bromoiodide emulsion containing 640 g. sucrose, 162 g. ascorbic acid, 30 g. 1-phenyl-3-pyrazolidone, 36 g. sodium sulfite, 540 g. sodium metaborate octahydrate, 12 g. potassium bromide and 117.6 g. sodium thiosulfate pentahydrate (Na S O -5H O) per mole silver halide was coated on single weight paper stock at a coverage of approximately 1600 ft. per mole silver halide, and then air dried. A control coating with the sodium thiosulfate omitted was made. An imagewise exposed strip of the coating containing sodium thiosulfate, when subjected to air saturated with water at 99 C. for 1 second, gave a legible print. The control coating required a processing time, and the background density of the print was 0.18 higher than that of the print containing sodium thiosulfate. Detailed sensitometric data appear in the following table:

Processing Nazsam. 5H2O time, 1 Relative (g./mole agX) seconds Speed D min 1 Air saturated with moisture at 99 C.

EXAMPLE 4 A gelatino-silver bromoiodide emulsion containing 640 g. sucrose, 162 g. ascorbic acid, 30 g. l-phenyl-3-pyrazolidone, 36 g. sodium sulfite, 540 g. sodium metaborate octahydrate, 12 g. potassium bromide, 157 g. sodium thiosulfate pentahydrate (Na S O -SH O) and 10 g. l-phenyI-S-mercaptotetrazole per mole of silver was coated on single weight paper stock at a coverage of approximately 1600 sq. ft. per mole of silver halide and then air dried. A 35 mm. wide control strip of the above coating was given an imagewise exposure and then processed at a paper travel speed of /2 ft. per min. by means of the processor described in the Stewart U.S. patent application Ser. No. 147,899 filed Oct. 6, 1961 (an apparatus including a convexly curved heated metal surface containing a plurality of transverse grooves adapted to trap moisture driven out of paper passed over the surface) operating at a temperature of 150 C. The coated side of a similar strip, after imagewise exposure, was laminated to an adhesive tape similar to that described in Example 2 and processed in a similar manner. The following data were obtained.

Samples similar to those described above were also, after an imagewise exposure, processed at the paper speeds listed below in an apparatus similar to the one described above in this example but which was additionally equipped with a moisture-saturated wick extending from a reservoir of water into a steam chamber operating at a temperature of 105 C. to convert the water in the Wick to steam. This steam can be conducted to the transverse grooves in the convexly curved heated metal surface by means of perforations extending through the metal surface from the steam chamber which may be at the back of said metal surface. Or the heated metal surface could be formed from a block of one of the commercially available sintered porous metals to overcome the problem of perforating the metal block to permit transfer of the steam from the back surface to the convexly curved surface of the same. The following data apply.

The invention has been described in considerable detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

What I claim is:

1. A non-light exposed light-sensitive element containing a small amount of moisture and comprising a support having thereon a silver halide emulsion layer, a silver halide developing agent and an alkaline material being integral with and contiguous to the silver halide and an integral flexible transparent layer resistant to penetration by water vapor as an outermost layer to seal said moisture in said element.

2. The element of claim 1 wherein the developing agent is present in the emulsion layer and the alkali in a layer separate from the emulsion layer.

3. The element of claim 1 wherein the developing agent is present in the emulsion layer and the alkali in a layer overlying the emulsion layer.

4. A light-sensitive element of claim 1 in which the support is paper.

5. A non-light-exposed light-sensitive element containing a small amount of moisture and comprising a paper support having thereon a silver halide emulsion layer, at least about 5 gms. per mole silver halide of a 3-pyrazolidone silver halide developing agent, a non-reducing saccharide and an alkaline material being integral With and continguous to the silver halide, and an integral flexible transparent layer resistant to penetration by water vapor adhered to the outer surface of the emulsion layer.

6. A non-light-exposed light-sensitive element containing a small amount of moisture and comprising a paper support having thereon a silver halide emulsion layer, at least about 15 gms. per mole of silver halide of a silver halide developing agent of the class consisting of polyhydric phenol and ascorbic acid developing agents, at at least about 5 gms. per mole silver halide of a 3-pyrazolidone silver halide developing agent and an alkaline material being integral with an contiguous to the silver halide, and an integral flexible transparent layer resistant to penertation by water vapor adhered to the outer surface of the emulsion layer.

7. A non-light exposed light-sensitive element containing a small amount of moisture and comprising a paper support having thereon a silver halide emusion layer, at least about 15 gms. per mole silver halide of a p0lyhydric phenol developing agent, at least about 5 gms. per mole silver halide of a 3-pyrazolidone silver halide developing agent and an alkaline material being integral with and contiguous to the silver halide, and an integral flexible transparent layer resistant to penertation by water vapor adhered to the outer surface of the emulsion layer.

8. A non-light exposed light-sensitive element containing a small amount of moisture and comprising a paper support having thereon a silver halide emulsion layer, at least about 15 gms. per mole silver halide of ascorbic acid, at least about 5 gms. per mole silver halide of a 3- pyrazolidone silver halide developing agent and an alkaline material being integral with and contiguous to the silver halide and an integral flexible transparent layer resistant to penetration by water vapor adhered to the outer surface of the emulsion layer.

9. The element of claim 3 further containing ascorbic acid integral with and contiguous to the silver halide.

10. The element of claim 1 wherein the alkaline material is an alkali metal metaborate.

11. A photographic process comprising exposing to a subject a light-sensitive photographic element containing water, including a support having thereon a photosensitive emulsion layer, a developing composition for said photosensitive emulsion layer, and a flexible transparent layer substantially impermeable to water vapor adhered to the outer surface of the emulsion layer, and heating said element whereby said water activates the developer composition until an image is obtained in the emulsion layer.

12. A photographic process comprising exposing to a subject a light-sensitive photographic element containing water, including a support having thereon a silver halide emulsion layer, a silver halide developing composition, and a flexible transparent layer substantially impermeable to water vapor adhered to the outer surface of the emulsion layer, and heating said element whereby said Water activates the developer composition until a silver image is obtained in the emulsion layer.

13. A photographic process comprising exposing to a subject a light-sensitive photographic element including a support having thereon a silver halide emulsion layer, a halide developing agent and an alkaline material being integral with and contiguous to the silver halide and an integral flexible transparent layer substantially impermeable to water vapor adhered to the outer surface of the emulsion layer, and heating said element containing a small amount of moisture until a silver image is obtained in the emulsion layer.

14. A photographic process which comprises exposing to a subject a light-sensitive element containing a small amount of moisture and comprising a paper support having thereon a silver halide emulsion layer, a 3-pyrazolidone silver halide developing agent and an alkaline material being integral with and contiguous to the silver halide, and an integral flexible transparent layer resistant to penetration by water vapor adhered to the outer surface of the emulsion layer, and heating said element until a silver image is obtained in the emulsion layer.

15. A photographic process which comprises exposing to a subject a light-sensitive element containing a small amount of moisture and comprising a paper support having thereon a silver halide emulsion layer, at least about 5 gms. per mole silver halide of a 3-pyrazolidone silver halide developing agent, a non-reducing saccharide and an alkaline material being integral with and contiguous to the silver halide, and an integral flexible transparent layer resistant to penetration by water vapor adhered to the outer surface of the emulsion layer, and heating said element until a silver image is obtained in the emulsion layer.

16. A photographic process which comprises exposing to a subject a light-sensitieve element containing a small amount of moisture and comprising a paper support having thereon a silver halide emulsion layer, at least about 15 gms. per mole of silver halide of a silver halide developing agent of the class consisting of polyhydric phenol and ascorbic acid developing agents, at least about 5 gms. per mole silver halide of 3-pyrazolidone silver halide developing agent and an alkaline material being integral with and contiguous to the silver halide, and an integral flexible transparent layer resistant to penetration by water vapor adhered to the outer surface of the emulsion layer, and heating said element until a silver image is obtained in the emulsion layer.

17. A photographic process which comprises exposing to a subject a light-sensitive element containing a small amount of moisture and comprising a paper support having thereon a silver halide emulsion layer, at least about 15 gms. per mole silver halide of a polyhydric phenol developing agent, at least about 5 gms. per mole silver halide of a 3-pyrazolidone silver halide developing agent and an alkaline material being integral with and contiguous to the silver halide, and an integral flexible transparent layer resist to penetration by water vapor adhered to the outer surface of the emulsion layer, and heating said element until a silver image is obtained in the emulsion layer.

18. A photographic process which comprises exposing to a subject a light-sensitive element containing a small amount of moisture and comprising a paper support having thereon a silver halide emulsion layer, at least about 15 gms. per mole silver halide of ascorbic acid, at least about 5 gms. per mole silver halide of a 3-pyrazolidone silver halide developing agent and an alkaline material being integral with and contiguous to the silver halide and an integral flexible transparent layer resistant to penetration by water vapor adhered to the outer surface of the emulsion layer, and heating said element until a silver image is obtained in the emulsion layer.

19. The process of claim 11 wherein the element further contains ascorbic acid integral with and contiguous to the silver halide.

References Cited UNITED STATES PATENTS 3,248,219 4/1966 Jacobs 96-76 NORMAN G. TORCHIN, Primary Examiner C. E. DAVIS, Assistant Examiner US. Cl. X.R.

223?" UNITED. STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,L.68,66L1 Dated 9/23/69 Inventor) Paul H, Stewart It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

F601. 10, line 50, between "with" and "contiguous", delete "an" and substitute in its place --and-; line 52, between "to" and "by", delete "penertation" and substitute in its place --penetration-; line 62, between "to" and "by", delete "penertation' and substitute in its place -penetration--.

Col. 1 1 lines Zip/25, between "emulsion layer, a" and "halide developing", add --silveI---.

Col. 12, line 2, between "light-" and "element", delete "sensitieve" and substitute in its place --sensitive--; line 21 between "layer" and "to", delete "resist" and substitute in its place -resistant.

SIGNED *N'D SEALED Edfidmnmh- Atlestmg' Officer un.

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